Graded bandgap single-crystal emitter heterojunction bipolar transistor
US5352912A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 13, 1991 |
| Grant date | Oct 4, 1994 |
| Priority date | — |
| Expiry date | Nov 13, 2011 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S438/936
Abstract
A heterojunction bipolar transistor having a single-crystal emitter with reduced charge storage and acceptable current gain is described herein. The heterojunction transistor comprises a collector region, a base region formed on the collector region, and a single-crystal emitter region grown on the base region by low temperature epitaxy. During the formation of the base region, a graded profile of 5-23% germanium is added to the base, as the distance to the collector region decreases, thereby decreasing the base bandgap as it approaches the collector region. Further, during the formation of the emitter region, a graded profile of 0-20% germanium is added to the emitter as the distance from the emitter-base junction increases. Thus, the emitter bandgap decreases as it moves farther from the emitter-base junction. The result of the above grading profiles is that the emitter bandgap is narrower at the emitter contact than the base bandgap at the emitter-base junction.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.